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July 11, 2013

Wind Power Has Minimal Impact On Greater Prairie Chickens

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redOrbit Staff & Wire Reports - Your Universe Online

Wind power development does not strongly disrupt greater prairie chicken populations and has no impact on nest site selection, female reproductive effort, nesting success or the overall population of these grassland birds, Kansas State University ecologists reported on Wednesday.

These conclusions were based on an investigation of the impacts of wind power development on the demography, movements, and population genetics of greater prairie-chickens (Tympanuchus cupido) at three Kansas sites - one of which was developed for wind power - during a 7-year period.

Led by Kansas State Biology Professor Brett Sandercock, the researchers discovered wind turbines have little effect on greater prairie chickens, and that the birds are more affected by rangeland management practices and the availability of native prairie and vegetation cover at nest sites.

The study did find some slightly negative impacts from wind power development, including a trend for reductions in lek site persistence near turbines. Positive impacts included an increase in female survival rates after wind turbines were installed.

But the study found the strongest correlates of overall female reproductive success were the availability of native prairie and vegetative cover at the nest site, the researchers said.

Sandercock said he and his team were part of a consortium of stakeholders who studied how wind power projects influence grassland birds.

"We had a lot of buy-in from stakeholders and we had an effective oversight committee," he said.

"The research will certainly aid with wind power site guidelines and with the development of mitigation strategies to enhance habitat conditions for the greater prairie chicken."

The greater prairie chicken was once abundant across the central Plains, although populations have declined due to habitat loss and human development. The chickens now are mainly found in the Great Plains in Kansas - particularly the Smoky Hills and the Flint Hills - where the largest tracts of prairie remain.

The researchers began their study in 2006 with three field sites selected for wind development - a site in the Smoky Hills in north central Kansas, a site in the northern Flint Hills in northeastern Kansas and a site in the southern Flint Hills in southern Kansas.

The Smoky Hills site - the Meridian Way Wind Power Facility near Concordia - was developed into a wind energy site, giving researchers an ideal opportunity to observe greater prairie chickens before, during and after wind turbine construction.

The team studied the chickens for seven breeding seasons and captured nearly 1,000 total male and female birds around lek sites, which are communal areas where males gather and make calls to attract females. Females mate with the males and then hide nests in tall prairie grass.

The researchers investigated many different features of prairie chickens and their biology, including patterns of nest site selection, reproductive components, survival rates and population viability.

"We don't have evidence for really strong effects of wind power on prairie chickens or their reproduction," Sandercock said.

"We have some evidence for females avoiding the turbines, but the avoidance within the home range doesn't seem to have an impact on nest site selection or nest survival."

Sandercock said he was somewhat surprised at the findings, because similar studies had shown that oil and gas development affect prairie chickens.

With wind power development, however, the researchers observed the unexpected result of female survival rates increasing after wind turbines were installed. This might be attributed to wind turbines keeping predators away from nest sites, Sandercock said.

Female mortality rates are highest during the breeding season because females are more focused on protecting clutches than avoiding predators, he added.

"What's quite typical for these birds is most of the demographic losses are driven by predation. We can say that with confidence."

"What's a little unclear from our results is whether that increase in female survivorship was due to the effects of wind turbines on predators."

The researchers also found conservation management practices appear to have the strongest effect on the birds.

Since prairie chickens are ground-nesting birds and need adequate cover for their nests to survive, grazing and fire management practices can affect how much nesting cover is available for chickens, Sandercock said.

"A lot of what drives nest survival is the local conditions around the nest.

"Do they have good nesting cover or not? Our results are important because they suggest ways for mitigation."

The researchers are now conducting follow-up studies to test mitigation strategies that may improve habitat conditions for prairie chickens.